[dpdk-dev] [PATCH] vhost: fix connect hang in client mode

[Yuanhan Liu]

On Thu, Jul 21, 2016 at 11:21:15AM +0300, Ilya Maximets wrote:
> If something abnormal happened to QEMU, 'connect()' can block calling
> thread (e.g. main thread of OVS) forever or for a really long time.
> This can break whole application or block the reconnection thread.
> 
> Example with OVS:
> 
> 	ovs_rcu(urcu2)|WARN|blocked 512000 ms waiting for main to quiesce
> 	(gdb) bt
> 	#0  connect () from /lib64/libpthread.so.0
> 	#1  vhost_user_create_client (vsocket=0xa816e0)
> 	#2  rte_vhost_driver_register
> 	#3  netdev_dpdk_vhost_user_construct
> 	#4  netdev_open (name=0xa664b0 "vhost1")
> 	[...]
> 	#11 main
> 
> Fix that by setting non-blocking mode for client sockets for connection.
> 
> Fixes: 64ab701c3d1e ("vhost: add vhost-user client mode")

Thanks for spotting and fixing yet another bug!

>  
> +static int
> +vhost_user_connect_nonblock(int fd, struct sockaddr *un, size_t sz)

I don't quite understand why this is needed: connect() with O_NONBLOCK
flag set is not enough?

	--yliu